As oil producing fields are gradually becoming more mature, requests for more advance drilling techniques and equipment to handle the depleted reservoirs are becoming more common. For example, older, more mature oil reservoirs may include fractures in the drilled walls of the well bore. There are gas fields where production was started while the development of the field was still ongoing. In such fields, depletion due to production and the fact that pressure depleted at a slightly higher rate than expected, resulted in a reservoir that is more easily fractured. Managed pressure drilling (MPD) is an example of advanced tools and equipment that focuses on preventative treatment of induced and natural fractures in the drilled well bore. Further, to continue to produce from the reservoir, the fractures are bridged using various types of bridging material.
There is also a growing demand within the industry to find equipment that can run real time measurements of particle size distribution to improve control of physical conditions within a reservoir with addition of lost circulation material (LCM) and to maintain this optimized particle concentration and thereby prevent losses. Typically, particle size distribution (PSD) is measured on a sample of a wellbore fluid for which PSD is being determined. That is, a sample of drilling fluid is taken out of the flow line and the PSD of the sample is determined.
Conventional processes and/or equipment for determining PSD employ laser diffraction methods to determine the PSD of the sample. Laser diffraction based particle size analysis relies on the fact that particles passing through a laser beam will scatter light at an angle that is directly related to their size. This method typically assumes that all particles are spherical regardless of actual shape of the particles. As particle size decreases, the observed scattering angle increases logarithmically. Scattering intensity is also dependent on particle size, diminishing with particle volume. Large particles therefore scatter light at narrow angles with high intensity whereas small particles scatter at wider angles but with low intensity. In laser diffraction, particle size distributions are calculated by comparing the sample's scattering pattern with an appropriate optical model by exploiting the above-described behavior of the particles that pass through the laser beam. Further, with laser diffraction, normalized values of particle size distribution are reported. In a normalized system, changes in one area may change the distribution in other regions completely.
Often times, sampling of the fluid in the flow line leads to inaccuracy in the PSD measurement of materials in the fluid, because the sample is often diluted in order to use laser diffraction methods to determine PSD. Dilution of the sample often breaks up conglomerated particles, thereby altering the sample before PSD measurements are taken. Therefore, the PSD of the sample may not be an accurate representation of the PSD of the flow line.